SALT LAKE CITY--Flash floods killed 12 people near Utah's border with Arizona when a "large wall of water and debris" triggered by heavy rain pounding nearby canyons swept them away in their cars, officials said on Tuesday. In Zion National Park to the north, three people died and four were missing after going to explore canyons, officials said. "Another tragedy for our state. Reeling right now," Utah Lieutenant Governor Spencer Cox said on Twitter. In the small city of Hildale, Utah, hundreds of volunteers were helping search for one person still missing, Washington County officials said, after floodwaters swept through streets. "It was an act from God," Hildale Mayor Phillip Barlow told reporters of Monday's tragedy, according to the Deseret News. "This is something we can't control. ... It happened too fast." Crews have worked since Monday evening monitoring flood crossings and searching the banks of Short Creek amid sporadic rain showers. Contractors using heavy equipment have worked to clear thousands of tons of mud and debris, and the National Guard has been called in to help with the cleanup. "In the flash flooding two occupied vehicles were hit by a large wall of water and debris at the Canyon Street Maxwell Crossing and were carried into the Flood," Washington County officials said in a statement overnight. Utah Governor Gary Herbert said he was "heartbroken," and that the state has offered its full resources to Hildale to aid the search and rescue effort. Hildale, home to fewer than 3,000 people, is twinned with Colorado City, across the border in Arizona. Both cities are home to the polygamous Fundamentalist Church of Jesus Christ of Latter-day Saints. That sect is not affiliated with the Salt Lake City-based Church of Jesus Christ of Latter-day Saints, which renounced polygamy in 1890.